| Message ID | 20211112054510.2667030-1-songliubraving@fb.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | x86/perf: fix snapshot_branch_stack warning in VM | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On 12/11/2021 1:45 pm, Song Liu wrote: > When running in VM intel_pmu_snapshot_branch_stack triggers WRMSR warning > like: > > [ 252.599708] unchecked MSR access error: WRMSR to 0x3f1 (tried to write 0x0000000000000000) at rIP: 0xffffffff81011a5b (intel_pmu_snapshot_branch_stack+0x3b/0xd0) > [ 252.601886] Call Trace: > [ 252.602215] <TASK> > [ 252.602516] bpf_get_branch_snapshot+0x17/0x40 > [ 252.603109] bpf_prog_5c58f41f99af93ce_test1+0x33/0xd54 > [ 252.603777] bpf_trampoline_15032502913_0+0x4c/0x1000 > [ 252.604435] bpf_testmod_loop_test+0x5/0x20 [bpf_testmod] > [ 252.605127] bpf_testmod_test_read+0x8f/0x3b0 [bpf_testmod] > [ 252.605864] ? bpf_testmod_loop_test+0x20/0x20 [bpf_testmod] > [ 252.606612] ? __kasan_kmalloc+0x84/0xa0 > [ 252.607146] ? lock_is_held_type+0xd8/0x130 > [ 252.607736] ? sysfs_kf_bin_read+0xbe/0x110 > [ 252.608513] ? bpf_testmod_loop_test+0x20/0x20 [bpf_testmod] > [ 252.609332] kernfs_fop_read_iter+0x1ac/0x2c0 > [ 252.609901] ? kernfs_create_link+0x110/0x110 > [ 252.610509] new_sync_read+0x25a/0x380 > [ 252.610994] ? __x64_sys_llseek+0x1e0/0x1e0 > [ 252.611538] ? rcu_read_lock_sched_held+0xa1/0xd0 > [ 252.612165] ? find_held_lock+0xac/0xd0 > [ 252.612700] ? security_file_permission+0xe7/0x2c0 > [ 252.613326] vfs_read+0x1a4/0x2a0 > [ 252.613780] ksys_read+0xc0/0x160 > [ 252.614218] ? vfs_write+0x510/0x510 > [ 252.614684] ? ktime_get_coarse_real_ts64+0xe4/0xf0 > [ 252.615423] do_syscall_64+0x3a/0x80 > [ 252.615886] entry_SYSCALL_64_after_hwframe+0x44/0xae > [ 252.616553] RIP: 0033:0x7f62aa7f08b2 > [ 252.617011] Code: 97 20 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b6 0f 1f 80 00 00 00 00 f3 0f 1e fa 8b 05 96 db 20 00 85 c0 75 12 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 41 54 49 89 d4 55 48 89 > [ 252.619333] RSP: 002b:00007ffe72c83628 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > [ 252.620252] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f62aa7f08b2 > [ 252.621138] RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000028 > [ 252.622035] RBP: 00007ffe72c83660 R08: 0000000000000000 R09: 00007ffe72c83507 > [ 252.622951] R10: 0000000000000000 R11: 0000000000000246 R12: 000000000040d090 > [ 252.623890] R13: 00007ffe72c83900 R14: 0000000000000000 R15: 0000000000000000 > [ 252.624829] </TASK> > > This can be triggered with BPF selftests: > > tools/testing/selftests/bpf/test_progs -t get_branch_snapshot > > This warning is caused by __intel_pmu_pebs_disable_all() in the VM. Since > it is not necessary to disable PEBs for LBR, remove it from > intel_pmu_snapshot_branch_stack and intel_pmu_snapshot_arch_branch_stack. > > Fixes: c22ac2a3d4bd ("perf: Enable branch record for software events") > Cc: Like Xu <like.xu.linux@gmail.com> > Cc: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Song Liu <songliubraving@fb.com> Tested-by: Like Xu <likexu@tencent.com> I guess bpf users will be happier with the usages of Intel PT snapshot mode. > --- > arch/x86/events/intel/core.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c > index 42cf01ecdd131..ec6444f2c9dcb 100644 > --- a/arch/x86/events/intel/core.c > +++ b/arch/x86/events/intel/core.c > @@ -2211,7 +2211,6 @@ intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int > /* must not have branches... */ > local_irq_save(flags); > __intel_pmu_disable_all(false); /* we don't care about BTS */ > - __intel_pmu_pebs_disable_all(); > __intel_pmu_lbr_disable(); > /* ... until here */ > return __intel_pmu_snapshot_branch_stack(entries, cnt, flags); > @@ -2225,7 +2224,6 @@ intel_pmu_snapshot_arch_branch_stack(struct perf_branch_entry *entries, unsigned > /* must not have branches... */ > local_irq_save(flags); > __intel_pmu_disable_all(false); /* we don't care about BTS */ > - __intel_pmu_pebs_disable_all(); > __intel_pmu_arch_lbr_disable(); > /* ... until here */ > return __intel_pmu_snapshot_branch_stack(entries, cnt, flags); >
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index 42cf01ecdd131..ec6444f2c9dcb 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -2211,7 +2211,6 @@ intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int /* must not have branches... */ local_irq_save(flags); __intel_pmu_disable_all(false); /* we don't care about BTS */ - __intel_pmu_pebs_disable_all(); __intel_pmu_lbr_disable(); /* ... until here */ return __intel_pmu_snapshot_branch_stack(entries, cnt, flags); @@ -2225,7 +2224,6 @@ intel_pmu_snapshot_arch_branch_stack(struct perf_branch_entry *entries, unsigned /* must not have branches... */ local_irq_save(flags); __intel_pmu_disable_all(false); /* we don't care about BTS */ - __intel_pmu_pebs_disable_all(); __intel_pmu_arch_lbr_disable(); /* ... until here */ return __intel_pmu_snapshot_branch_stack(entries, cnt, flags);
When running in VM intel_pmu_snapshot_branch_stack triggers WRMSR warning like: [ 252.599708] unchecked MSR access error: WRMSR to 0x3f1 (tried to write 0x0000000000000000) at rIP: 0xffffffff81011a5b (intel_pmu_snapshot_branch_stack+0x3b/0xd0) [ 252.601886] Call Trace: [ 252.602215] <TASK> [ 252.602516] bpf_get_branch_snapshot+0x17/0x40 [ 252.603109] bpf_prog_5c58f41f99af93ce_test1+0x33/0xd54 [ 252.603777] bpf_trampoline_15032502913_0+0x4c/0x1000 [ 252.604435] bpf_testmod_loop_test+0x5/0x20 [bpf_testmod] [ 252.605127] bpf_testmod_test_read+0x8f/0x3b0 [bpf_testmod] [ 252.605864] ? bpf_testmod_loop_test+0x20/0x20 [bpf_testmod] [ 252.606612] ? __kasan_kmalloc+0x84/0xa0 [ 252.607146] ? lock_is_held_type+0xd8/0x130 [ 252.607736] ? sysfs_kf_bin_read+0xbe/0x110 [ 252.608513] ? bpf_testmod_loop_test+0x20/0x20 [bpf_testmod] [ 252.609332] kernfs_fop_read_iter+0x1ac/0x2c0 [ 252.609901] ? kernfs_create_link+0x110/0x110 [ 252.610509] new_sync_read+0x25a/0x380 [ 252.610994] ? __x64_sys_llseek+0x1e0/0x1e0 [ 252.611538] ? rcu_read_lock_sched_held+0xa1/0xd0 [ 252.612165] ? find_held_lock+0xac/0xd0 [ 252.612700] ? security_file_permission+0xe7/0x2c0 [ 252.613326] vfs_read+0x1a4/0x2a0 [ 252.613780] ksys_read+0xc0/0x160 [ 252.614218] ? vfs_write+0x510/0x510 [ 252.614684] ? ktime_get_coarse_real_ts64+0xe4/0xf0 [ 252.615423] do_syscall_64+0x3a/0x80 [ 252.615886] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 252.616553] RIP: 0033:0x7f62aa7f08b2 [ 252.617011] Code: 97 20 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b6 0f 1f 80 00 00 00 00 f3 0f 1e fa 8b 05 96 db 20 00 85 c0 75 12 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 56 c3 0f 1f 44 00 00 41 54 49 89 d4 55 48 89 [ 252.619333] RSP: 002b:00007ffe72c83628 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [ 252.620252] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f62aa7f08b2 [ 252.621138] RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000028 [ 252.622035] RBP: 00007ffe72c83660 R08: 0000000000000000 R09: 00007ffe72c83507 [ 252.622951] R10: 0000000000000000 R11: 0000000000000246 R12: 000000000040d090 [ 252.623890] R13: 00007ffe72c83900 R14: 0000000000000000 R15: 0000000000000000 [ 252.624829] </TASK> This can be triggered with BPF selftests: tools/testing/selftests/bpf/test_progs -t get_branch_snapshot This warning is caused by __intel_pmu_pebs_disable_all() in the VM. Since it is not necessary to disable PEBs for LBR, remove it from intel_pmu_snapshot_branch_stack and intel_pmu_snapshot_arch_branch_stack. Fixes: c22ac2a3d4bd ("perf: Enable branch record for software events") Cc: Like Xu <like.xu.linux@gmail.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Song Liu <songliubraving@fb.com> --- arch/x86/events/intel/core.c | 2 -- 1 file changed, 2 deletions(-)